It is known to use ball screw actuators to translate a rotational displacement into an axial displacement while minimising frictional losses. Ballscrew actuators are used in a variety of applications, including in aircraft and aircraft engines.
Ball screw actuators are generally lubricated in order to facilitate relative motion between the screw, nut and balls. It is desirable to seal the ballscrew actuator in such a way as to prevent the lubricant leaking, thereby to maximise the period between reapplications of the lubricant.
In addition, ballscrew actuators are often operated in adverse environmental conditions. External moisture or debris which enters the ballscrew assembly reduces the effectiveness of the actuator, and it is therefore also desirable to seal the assembly to prevent ingress of environmental elements.